Lately I've been noticing a strange musky smell in my bathroom that seems to be coming from nowhere. This is a spare bathroom that isn't used much, but a few months ago I did some work where I replaced the toilet and used two wax gaskets to seal it. If there was a leak there, wouldn't it smell like sewer gas? I also repainted the bathroom and put in new floor tile, so it's not like the room should smell old and raunchy. This is more of a strong plant smell. I caulked around the toilet at the floor and the smell is still there. I've stuck my head near every drain but the smell just seems to be in the air.
Any help would be appreciated.

I think water that stands in an unused toilet for too long can go bad. Try flushing it at least once a week whether you use it or not. Some of the automatic toilet cleaners might kill off what is creating the odor.

If you have a small leak where the toilet seals to the drain, you may not have enough waste leak out to give a sewer smell, but have enough water leak out to create mildew and a musty smell someplace hidden. If the new floor raised the toilet, the double wax ring may not have worked. I would look around for signs of a leak, underneath if possible. You may want to pull the toilet and see if it looks like it is leaking.

Tom has more experience on this stuff and may have a better idea.

I think water that stands in an unused toilet for too long can go bad.  Try flushing it at least once a week whether you use it or not.  Some of the automatic toilet cleaners might kill off what is creating the odor.  

If you have a small leak where the toilet seals to the drain, you may not have enough waste leak out to give a sewer smell, but have enough water leak out to create mildew and a musty smell someplace hidden.  If the new floor raised the toilet, the double wax ring may not have worked.  I would look around for signs of a leak, underneath if possible.  You may want to pull the toilet and see if it looks like it is leaking.  

Tom has more experience on this stuff and may have a better idea.  

Thanks for your response. Actually, the toilet and sink are used daily by my daughter. I should have said that only the tub is never used, due to a shower in the other bathroom. The new floor raised the toilet a bit above the floor flange, maybe a half inch at most, so the guy at the plumbing supply store suggested the double wax ring. I thought the caulking around the base of the toilet would prevent any smell, but I think you're right. I'm probably going to have to pull the toilet and check for leaks.

Hey Wiz, As usual, Labman gave you good advice. Let me add to it. Installing floor tile raised the bowl up from the closet flange. While two wax seals are good a wax seal with a plastic funnel is better. There is a possibility that the two seal can leak and cause mildew and mold under the base of the bowl. A wax seal with a funnel will remove any possibility of a seal leak. Most hardware stores carry them and they are cheap insurance against a leak. If, when you pull the bowl and find mold and mildew scrub the area with bleach and let dry before resetting the toilet. Don't forget to run water in the unused tub to prevent the trap from evaporating and letting sewer gas escape. Good luck, Tom

Hey Wiz,  As usual, Labman gave you good advice.  Let me add to it.  Installing floor tile raised the bowl up from the closet flange.  While two wax seals are good a wax seal with a plastic funnel is better.   There is a possibility   that the two seal can leak and cause mildew and mold under the base of the bowl.  A wax seal with a funnel will remove any possibility of a seal leak.  Most hardware stores carry them and they are cheap insurance against a leak.   If, when you pull the bowl and find mold and mildew scrub the area with bleach and let dry before resetting the toilet. Don't forget to run water in the unused tub to prevent the trap from evaporating and letting sewer gas escape.   good luck,  Tom

Thanks for the response, Speedball. I'll take your advice. I've been reading some horror stories on the 'net about the problems mold can cause. If mold is my problem, I definitely have to take care of it right away.

Fluidmaster makes a wax free bowl gasket set for just that situation. It's model 7500. I'm in the process of tiling a bathroom now and that's what I'm going to install.

Fluidmaster makes a wax free bowl gasket set for just that situation. It's model 7500. I'm in the process of tiling a bathroom now and that's what I'm going to install.

Thanks. If a leaky gasket is my problem I think I'll try that.

The Fluidmaster is a little bit more complicated but looks good. If you would like to know more about it click on http://www.fluidmaster.com/usa.html You must have Adobe Reader to download. Good luck and let us know how you make out. Tom

The Fluidmaster is a little bit more complicated but looks good.  If you would like to  know more about it click on       http://www.fluidmaster.com/usa.html   You must have Adobe Reader to download.  good luck and let us know how you make out.  Tom

Thanks for all your help, guys. I ended up removing the shutoff valve access door behind the tub. I was then able to use a mirror and flashlight to see under the toilet, and everything was as dry as a bone.
What I think happened is, when the toilet is flushed, sometimes there's a gurgling noise from the tub. Could be the water from the trap in the tub was being sucked out, allowing the funny smell to enter the room. So I run the water in the tub occasionally to make sure there's water in the trap. I haven't had the smell all weekend, plus I put a bowl of vinegar behind the toilet to clear the air.

Hi Wiz, "when the toilet is flushed, sometimes there's a gurgling noise from the tub." And with those words you have just told me what was wrong in the first place. You have a bathroom vent that's blocked. Could be a birds nest or a dead critter but somthing's up in there. When a toilet's flushed the water draining sets up a vacume. This is relieved by the vent off the lavatory. If that vent is blocked the system has to relieve itself. In this case the gurgling sound you hear is air being drawn through the water in the tub trap. To take care of this, go up on the roof, shine a light down the vent and check for debris. If you don't see anything then you must snake the vent out from the roof. I wish you had mentioned this at first but I'm glad you brought it up now. Good luck, Tom

Hi Wiz,  "when the toilet is flushed, sometimes there's a gurgling noise from the tub."  And with those words you have just told me what was wrong in the first place.  You have a bathroom vent that's blocked.  Could be a birds nest or a dead critter but somthing's up in there.  When a toilet's flushed the water draining sets up a vacume.  This is relieved by the vent off the lavatory.  If that vent is blocked the system has to relieve itself.  In this case the gurgling sound you hear is air being drawn through the water in the tub trap.  To take care of this, go up on the roof, shine a light down the vent and check for debris.  If you don't see anything then you must snake the vent out from the roof.  I wish you had mentioned this at first but I'm glad you brought it up now.  good luck, Tom

I never considered that the vent may be blocked. This bathroom was either installed before such things as building codes existed, or else they were just plain ignored, since the vent comes right out the side of the house, next to the bathroom window. But I'll have to get a ladder up there and check it out. Thanks again, Tom.